Design av en Relativistisk Magnetron för 2π-Mod till TE11 i X-Band : Analys av elektronbanor i resonanskaviteter och simulering av mikrovågsgenerering och propagering

High power microwaves (HPM) are waves with high power density that can be used to disrupt or destroy electronics from a distance. Relativistic magnetrons can generate HPM from electron-wave interaction. With output powers on a scale of 100 MW, they have a large effective range. The aim of this project was to develop a relativistic magnetron that resonates using the 2𝜋-mode and then converts it into a TE11-mode, with a frequency in the X-band (8 − 12 GHz). The starting point was the magnetron developed by the Swedish Defence Research Agency (FOI), which in originally resonates using a 𝜋-mode. Which wave mode that becomes excited depends on the dimensions of the interaction region, the applied voltage and the magnetic field strength. To understand how to excite the 2𝜋-mode, an analytical model was developed to calculate the orbit of an electron in a coaxial gap. Using the Hamiltonian for electrons in electromagnetic fields, expressions were derived for the radial position of the orbit apex, along with the magnitude of the electron velocity along the orbit. These were validated against numerical calculations using COMSOL Multiphysics. The diffraction output axially extracts the excited waves and converts them into a suitable output mode. Adaptations of the original diffraction output of the FOI-magnetron did not produce TE11 when fed with a 2𝜋-mode. An efficient conversion was discovered using a simple, smooth-walled diffraction output that produced an intermediate TE01. An added mode converter then converts TE01 into a linearly polarized TE11. Attempts to calculate the efficiency of the most promising magnetron designs were made with Particle-in-Cell (PIC) simulations. The smoothwalled diffraction output was joined with several variations of the interaction region. The 2𝜋-mode appeared in one variation at 7.1 GHz, which was lower than the expected cutoff at 8.3 GHz, with 0.3% efficiency. The main result of this work shows that it is possible to convert a 2𝜋-mode into TE11, by using a mode converter, in simulations using the Finite-Element-Method. However, in PIC-simulations, which include wave-particle interaction, the output mode is unclear. The reason for the lower than expected frequency and efficiency is also unclear. The electron-wave interaction in the interaction region is currently poorly understood, and requires further analysis and redesign using PIC-simulations.